1. Field of the Invention
This invention relates to an improvement in a process for stabilizing liquid hydrocarbon fuel by preventing the formation of solid oxidation products. More specifically, this invention relates to a process for regenerating for re-use any solid polymeric foam material which functions as a stability enhancing material for liquid hydrocarbon fuels such as diesel fuel and aviation jet fuel.
Middle distillate fuels including diesel fuel and aviation jet fuel have long been known to contain small concentrations of components which, when the fuel is stored for an extended period of time, form small spherical solid polymer particles which are insoluble in the fuel. Such solid particles have been known to clog fuel filters, interrupting fuel flow to engines during fueling operations, to foul engine heat exchangers, and to form deposits on injection nozzles in diesel and jet engines, distorting fuel spray patterns and, in severe cases, clogging the nozzle orifices and causing loss of power.
2. Description of the Prior Art
A number of methods for purifying and decolorizing liquid hydrocarbons as well as methods of regenerating the purifying agents are known.
U.S. Pat. No. 1,905,087 describes the regeneration of filtering or decolorizing agents such as fuller's earth, kieselguhr, bauxite, and charcoal used for the decolorization of oils, with methanol.
U.S. Pat. No. 2,687,990 describes a method of decolorizing petroleum fractions with cotton and the regeneration of the cotton with a polar solvent.
U.S. Pat. No. 3,472,786 discloses a method of regenerating a clay used for decolorizing petroleum fractions with alcohol vapor.
U.S. Pat. No. 4,152,249 discloses a process for purifying petroleum fractions by contact with solid adsorption resin such as phenol-formaldehyde. No resin regeneration process is disclosed.
U.S. Pat. No. 4,469,805 discloses a process in which spent filter clay used in the removal of contaminating organic compounds from petroleum distillates is regenerated by flushing with liquid methanol.
U.S. Pat. No. 4,912,873 discloses a process for purifying petroleum distillates or jet fuels with cross-linked acrylic aliphatic ester resin beads. No resin regeneration process is disclosed.
Power, A. J. and Solly, R. K. in Fuel, Vol. 69, October 1990, p. 1292 ff., describe the stabilization of middle distillate fuels by removal therefrom of particulate matter with flexible polyurethane foam. In a reduction to practice of this method, the foam is immersed in the diesel or jet fuel inside storage tanks. This prevents the formation of solid, fuel-insoluble particles in suspension in the liquid fuel for up to 2-3 years by absorbing the fuel-insoluble particles on the solid polymeric foam as they form. It allows fuel free of suspended particles to be drawn from the storage tank.
A drawback of this method is the fact that once the solid foam has absorbed its maximum capacity of fuel-insoluble solid particles, it must be removed from the storage tank and disposed of in a safe, economical, and environmentally acceptable manner. The customary method of removing the contaminated foam from the tank and disposing of it by incineration is uneconomical because it leads to the formation of oxides of nitrogen, sulfur dioxide and fly ash containing heavy metals which require costly stack gas scrubbers. Disposal in landfills may be prohibited by landfill disposal restrictions. Moreover, the removal of the contaminated foam from storage tanks is labor intensive and may expose workers to unacceptable levels of air contamination with fuel vapors.
It is the object of the present invention to provide an economical, safe and environmentally acceptable method of purifying and re-using contaminated foam.